Electrical properties of polycrystalline In-doped CdS thin films

Abstract

Polycrystalline In-doped CdS thin films have been deposited at 160, 220 and 250 degrees C by simultaneous evaporation of CdS and In from two crucibles. Films with In concentrations, N_In, in the 10¹⁷-10²¹ cm^-3 range have been characterised by Hall measurements. The conductivity, mobility and carrier concentration dependences on In concentration are reported. For the lower In concentrations, the conductivity is essentially determined by the deposition temperature. At N_In=8*10¹⁸ cm^-3 the conductivity presents a minimum, which is caused by a minimum in the mobility. The simultaneous rise of the carrier concentration is not sufficient to compensate the decrease of the mobility, contrary to the behaviour of polycrystalline silicon, where no conductivity minimum appears.